"An unclassified memo leaked this week says it is legal for the government to kill U.S. citizens abroad if it believes they are senior al-Qaeda leaders continually engaged in operations aimed at killing Americans, even if there is no evidence of a specific imminent attack. ...

"Brennan laid out the administration's policy for targeting al-Qaeda with lethal drone strikes ahead of the hearing, defending the use of such strikes but disavowing the harsh interrogation techniques used when he was at the CIA.

"In answers to pre-hearing questions released Wednesday by the Senate Intelligence Committee, Brennan said no further legislation was necessary to conduct operations against al-Qaeda wherever it's operating."